Pep Cell unproffesional

We bought a cellphone at PEP Cell Southdale Johannesburg; we were told it's a good phone as long as we have Wi-Fi although I do not know the make. The phone kept on getting stuck and buffering with the Wi-Fi at home. I signed the slip because I paid with my card. I was told if we were not happy, we should bring it back in seven days. We took it back today on Monday 18.12.2023 in the seven days. All of a sudden I actually signed for no refund on the phone. I understand you cannot refund the sim card that was given to you, but where does it state that you cannot give the phone back if you are not happy? I can only exchange it for something else. So, in other words, if I'm not happy with the second one, I have to keep on changing the phone. There is nothing on the phone because it is so slow we didn't even get a chance to load anything on there. The manager at the store was rude and started getting cheeky. Very unprofessional. I hope this will be resolved soon.